Every medical decision—whether to have chemotherapy, an X-ray, or surgery—is a risk, no matter which way you choose. Physician Paul A. Offit argues that, from the first blood transfusions four hundred years ago to the hunt for a COVID-19 vaccine, risk has been essential to the discovery of new treatments. More importantly, understanding the risks is crucial to whether, as a society or as individuals, we accept them. Told in Offit’s vigorous and rigorous style, this is an entertaining history of medicine. But it also lays bare the tortured relationships between intellectual breakthroughs, political realities, and human foibles. As we have learned from the COVID pandemic—the debates over lockdowns, masks, and vaccines—it’s all too easy to get everything wrong.